When I've had food poisoning the nausea always hit me about 12-24 hours later. My dad, being the geek he is, tested my vomit once for whatever it was that was making me ill. Turns out it was a cream based salad dressing that I'd eaten at a restaurant about 12 hours prior. The restaurant left it sitting out all day... Yuck. Anyway, food poisoning doesn't generally strike immediately following the meal in question, it's much more likely it was something you ate earlier but then started feeling sick directly after those meals. If that makes sense.